There has been known an inkjet recording device that forms images on a recording medium by ejecting ink stored in an ink tank through nozzles of a recording head. A feeding mechanism of this type of inkjet recording device typically includes a sheet feed section capable of accommodating a plurality of sheets of A4 size, for example; a sheet feed roller for feeding the sheets one at a time from the sheet feed section; a feeding roller for feeding the fed sheet to a position below a recording head; a pinch roller disposed in opposition to and pressed against the feeding roller; a discharge roller for discharging the sheet that has been formed with an image onto a discharge section; and a pinch roller (spur) arranged in opposition to and pressed against the discharge roller.
In this type of inkjet printer, a discrepancy between a theoretical paper feeding length of a recording medium and an actual paper feeding length thereof occurs. The theoretical paper feeding length refers to a paper feeding length obtained through calculation.
For example, if the radius of the feeding roller is “r”, then the theoretical paper feeding length by one-full rotation of the feeding roller is 2×π×r, wherein n is the circular constant. However, the feeding roller actually has the radius of r±δ due to manufacturing error of ±δ. Thus, the actual paper feeding length by one-full rotation of the feeding roller is 2×π×(r±δ). In other words, there is a difference of 2×π×(±δ) between the theoretical paper feeding length and the actual paper feeding length.
The discrepancy between the theoretical paper feeding length and the actual paper feeding length (hereinafter also referred simply as “discrepancy”) is also caused when the recording medium slips on the feeding roller and/or the discharge roller.
Further, the discrepancy occurs due to the backlash of the feeding roller, the discharge roller, and a mechanism, such as a gear coupling mechanism, for coupling a drive source, such as a DC motor, for driving these rollers.
For this reason, the feeding mechanism of the inkjet recording device includes a calibration means for calibrating a feeding amount of recording sheets so as to compensate the discrepancy between the theoretical paper feeding length and the actual paper feeding length (see, Japanese Patent-Application Publication Nos. 2002-254736 and 2001-88377).